1. Field of the Invention
The invention relates to a slider for a concealed type slide fastener in which a main body of the slider as an opening/closing device is not exposed outside when the slide fastener is closed, and more particularly, to a slider for a concealed type slide fastener which enables a smooth sliding operation even if a strong lateral pulling force is applied when the slide fastener is closed.
2. Description of the Related Art
Conventionally, this kind of the concealed type slide fastener has been often used for women's clothes, and in recent years, has advanced into other fields, for example, a field of passenger seat of automobile and train. In the passenger seat, its cushion body formed integrally with a frame in advance is covered with a seat cover. At this time, the dimensions of the seat cover are set smaller than the dimensions of the cushion body, so that the seat cover can cover the cushion body in a compressed state to suppress generation of looseness or deformation in the appearance shape as much as possible. Additionally, when a passenger is seated on the seat, the passenger seat is deformed elastically so as to correspond to a load distribution of the human body easily, and when he or she leaves the seat, it returns to its original shape, thereby preventing the seat from loosing its shape.
Usually, the seat cover comprises a sheet produced by uniting a surface skin layer, a thin elastic intermediate layer, and a rear face base fabric layer into a laminate by lamination processing, the surface skin layer constituted of natural leather or synthetic leather or woven or knitted fabric having various structures, the thin elastic intermediate layer constituted of a polyurethane foamed body sheet or the like, and the rear face base fabric layer constituted of a thin woven or knitted fabric obtained by weaving or knitting extremely fine threads. Usually, plural sheet pieces are cut from such a sheet so as to correspond to the shape of a passenger seat, and then, these sheet pieces are sewed together three-dimensionally in combination so as to produce a seat cover. However, if the entire seat cover is produced by sewing, the seat cover often cannot be applied to the cushion body of a seat having a complicated shape. Thus, conventionally, a portion not sewed is prepared, and after the seat cover is applied to the cushion body, the portion not sewed is sewed by hand.
However, the sewing by hand likely produces a difference in quality of a completed product or sewing time, because of a difference in skill of a sewing worker. Thus, in recent years, the slide fastener has been often used in part of the sewed portion of the seat cover, for example, along a bead portion, and particularly, a concealed type slide fastener whose slider main body is not exposed outside has been often used, in order to eliminating the hand sewing. As a result, all sewing operations can be carried out with a sewing machine, so that conventional faults based on a difference of skill are reduced largely, thereby leading to improvement of production efficiency.
In the concealed type slide fastener, as disclosed in for example, Japanese Patent Application Publication No. 50-25855, a pair of right and left first flanges each having an inverted L shaped section are provided along side edges of a lower plate of the slider body, the side edges being perpendicular to a slider sliding direction. The pair of first flanges comprise straight portions parallel as seen in a plan view, and expanded portions which are continued from the straight portions and expanded curvedly such that they depart from each other. A diamond having a substantially elliptic horizontal section is provided upwardly in a vertical direction at an end portion on an expanded side of the lower plate. A second flange is formed integrally on a top face of the diamond, and a gate-like pull tab attaching post is formed integrally on a top face of the second flange such that it extends in a sliding direction.
A pull tab is mounted onto the pull tab attaching post such that it can rotate freely back and forth in the sliding direction. The second flange comprises a substantially rectangular plate portion provided so as to be extended outwardly such that it surrounds a periphery of the diamond, and a wedge-like plate portion which is continued from the rectangular plate portion and provided so as to be extended toward a gap between the straight portions of the first flange with its front end formed sharply. Here, an opening at the end portion on a diamond side is called a shoulder mouth, and an opening on the opposite side to the diamond is called a rear mouth. A space formed by the first flange, the diamond and the second flange serves as a guide passage for a coupling element row, and a space formed between the first flange and the second flange serves as a guide gap for the fastener tape.
On the other hand, in fastener stringers in which a slider having such a configuration is inserted, a number of coupling elements are attached by sewing along opposing side edges of the pair of fastener tapes with coupling heads located inside, respectively. Element attachment edge portions of the pair of fastener stringers obtained in this way are folded back into a U shape such that the coupling heads of the coupling elements project outwardly along the element attachment edge portions. The folded shape is fixed by thermal setting. The slider is loaded on the pair of fastener stringers having such a structure, with the coupling heads of the elements opposing each other, from the shoulder mouth of the slider, and in addition, the folded portion of the fastener tape extended out from a tape guide gap between the first and second flanges, so that the slider is inserted in the fastener stringers to complete a concealed type slide fastener.
When the conventional concealed type slide fastener with the slider inserted therein, the slider having the above-described configuration, is applied to a seat cover of a passenger seat of an automobile or the like, and finally the slide fastener is closed, a strong laterally pulling force is applied to the fastener stringer in the vicinity of the slider because the seat cover is formed in a smaller dimension than the external dimension of the cushion body. The strong laterally pulling force raises the coupling element row due to a structure specific to the above-described concealed type slide fastener. Particularly in the conventional slider, the second flange having substantially the same thickness as the first flange is extended from the end face on the shoulder mouth of the diamond to the right and left side faces.
Each element to be introduced to the shoulder mouth while receiving a laterally pulling force at a portion near the shoulder mouth of the second flange is raised until it is substantially at right angle with respect to the tape face of the fastener tape. Until the connecting portion of each element rides over the top face of the lower plate of the slider, the element is introduced into an element guide passage of the slider in advance and receives a tilting by a preceding element tilted by contact with the first flange, the diamond and the upper plate portion of the second flange, and a relative pulling force of the fastener tape based on the sliding operation of the slider.
For this reason, a connecting portion of each element is often nipped in between the first and second flanges because the element is not tilted sufficiently when the connecting portion of each element rides over the top face of the lower plate of the slider, thereby disabling the sliding of the slider. If attempt is made to try to slide the slider forcibly, not only the element is damaged by the laterally pulling force, but also the folded edge of the fastener tape can be broken.
Particularly, the phenomenon that the element is nipped as described above is often found in concealed type slide fastener with independent elements in which respective elements are attached independently to an element attachment edge portion of a fastener stringer by injection molding. If speaking specifically, for example, in a concealed type slide fastener in which coil-like elements are attached to the fastener stringers, the respective elements are formed continuously with the elements located back and forth. For this reason, when the slider is slid, each element receives a force of tilting by a preceding element introduced into an element guide passage of the slider in advance.
However, a concealed type slide fastener in which respective elements are formed independently has such a problem that the element is nipped in between the first flange and the second flange because an influence of a tilting force applied to each element by a preceding element is small and the tilting of each element is very small.